Integration of disparity and velocity information for haptic and perceptual judgments of object depth

Do reach-to-grasp (prehension) movements require a metric representation of three-dimensional (3D) layouts and objects? We propose a model relying only on direct sensory information to account for the planning and execution of prehension movements in the absence of haptic feedback and when the hand is not visible. In the present investigation, we isolate relative motion and binocular disparity information from other depth cues and we study their efficacy for reach-to-grasp movements and visual judgments. We show that (i) the amplitude of the grasp increases when relative motion is added to binocular disparity information, even if depth from disparity information is already veridical, and (ii) similar distortions of derived depth are found for haptic tasks and perceptual judgments. With a quantitative test, we demonstrate that our results are consistent with the Intrinsic Constraint model and do not require 3D metric inferences (Domini, Caudek, & Tassinari, 2006). By contrast, the linear cue integration model (Landy, Maloney, Johnston, & Young, 1995) cannot explain the present results, even if the flatness cues are taken into account.     

Do we perceive a flattened world on the monitor screen?

The current model of three-dimensional perception hypothesizes that the brain integrates the depth cues in a statistically optimal fashion through a weighted linear combination with weights proportional to the reliabilities obtained for each cue in isolation (Landy, Maloney, Johnston, & Young, 1995). Even though many investigations support such theoretical framework, some recent empirical findings are at odds with this view (e.g., Domini, Caudek, & Tassinari, 2006). Failures of linear cue integration have been attributed to cue-conflict and to unmodelled cues to flatness present in computer-generated displays. We describe two cue-combination experiments designed to test the integration of stereo and motion cues, in the presence of consistent or conflicting blur and accommodation information (i.e., when flatness cues are either absent, with physical stimuli, or present, with computer-generated displays). In both conditions, we replicated the results of Domini et al. (2006): The amount of perceived depth increased as more cues were available, also producing an over-estimation of depth in some conditions. These results can be explained by the Intrinsic Constraint model, but not by linear cue combination.     

3-D structure perceived from dynamic information: a new theory

Image movement provides one of the most potent two-dimensional cues for depth. From motion cues alone, the brain is capable of deriving a three-dimensional representation of distant objects. For many decades, theoretical and empirical investigations into this ability have interpreted these percepts as faithful copies of the projected 3-D structures. Here we review empirical findings showing that perceived 3-D shape from motion is not veridical and cannot be accounted for by the current models. We present a probabilistic model based on a local analysis of optic flow. Although such a model does not guarantee a correct reconstruction of 3-D shape, it is shown to be consistent with human performance.     

Temporal integration in structure from motion

A temporal integration model is proposed that predicts the results reported in 4 psychophysical experiments. The main findings were (a) the initial part of a structure-from-motion (SFM) sequence influences the orientation evoked by the final part of that sequence (an effect lasting for more than 1 s), and (b) for oscillating SFM sequences, perceived slant is affected by the oscillation frequency and by the sign of the final gradient. For contracting optic flows (i.e., rotations away from the image plane), the sequence with the lowest oscillation frequency appeared more slanted; for expanding optic flows (i.e., rotations toward the image plane), the sequence with the highest oscillation frequency appeared more slanted.     

The Validity of the Employment Interview: A Meta-Analysis

The interview is the most widely used personnel selection method, but has revealed low reliability and validity compared with other selection methods (Mayfield 1964; Ulrich and Trumbo 1965; Schmitt 1976; Arvey 1979). Thirty-one studies on the validity of the interview were meta-analyzed. The result was an average validity coefficient of .27. The estimated true validity of the interview was calculated to be .38. These values indicated that the interview has moderate validity as a personnel selection device. Six characteristics of the interview were also examined in relation to the validity of the interview: structure of the interview; number of interviewers; length of the interview; gender of the applicant pool; blue-collar/white-collar jobs; and use of college students versus job applicants. The six study characteristics accounted for 30.9% of the variance in the validity of the interview. Structure of the interview appeared to be the only characteristic that moderated the validity of the interview. The relationship of this study to other meta-analyses of the employment interview is discussed.     

Clinical versus actuarial prediction: a review of the literature.

Decisions made by psychologists can have considerable consequences on people's lives. Their decisions could be based on clinical judgment or empirically derived formulas. These two alternatives created a controversy concerning clinical and actuarial prediction. This controversy has been in existence for almost 70 years. During this time hundreds of articles have been published on this topic. This paper contains a review of the findings and issues on clinical versus actuarial prediction. The main conclusions are that (1) linear models are superior to other mathematical models of human judgment, (2) actuarial methods are more accurate than clinical prediction in many situations, (3) human judgment is flawed, and (4) actuarial methods are rarely employed in practice for a variety of reasons.     

Do Supervisors and Subordinates See Eye-to-Eye on Job Enrichment?

The Social Information Processing Model states that employees' perceptions of their job characteristics are influenced in part by others (e.g., supervisors). This study compared supervisors' and their subordinates' perceptions of the subordinates' job enrichment. The convergence of these perceptions were then examined in relation to the subordinates' job satisfaction, performance, and organizational commitment. Fifty-two supervisor-subordinate pairs from an university in the northeastern United States were the subjects in this study. Results indicted that: (1) supervisors and their subordinates perceive subordinates' job characteristics differently, and (2) the supervisors' perceptions have limited relationships with critical work outcomes. Implications of these findings are discussed.     

The intrinsic constraint model for stereo-motion integration

How the visual system integrates the information provided by several depth cues is central for vision research. Here, we present a model for how the human visual system combines disparity and velocity information. The model provides a depth interpretation to a subspace defined by the covariation of the two signals. We show that human performance is consistent with the predictions of the model, and compare them with those of another theoretical approach, the modified weak-fusion model. We discuss the validity of each approach as a model for human perception of 3-D shape from multiple cues to depth.     

Task-Oriented Versus Other-Referenced Competition: Differential Implications for Children's Peer Relations1

We conceptualized a multidimensional construct of competitiveness among children. In our model, competing in order to achieve task mastery is distinct from competition motivated by social comparison. Competition is further differentiated by domain, with a distinction between the physical and cognitive domains. Peer- and self-report measures were developed to measure these dimensions. In general, these factors emerged as well-defined and as having somewhat different implications for peer relations. There was little concordance between the peer-nomination and self-report data. The peer nominations indicated that task-oriented competition was generally associated with acceptance and prosocial behavior, whereas other-directed competition was generally associated with being liked less and being seen as aggressive. There was little corroboration of these links in the analyses based on the self-report data.     

Discriminating constant from variable angular velocities in structure from motion

We investigated accuracy in discriminating between constant and variable angular velocities for orthographic projections of three-dimensional rotating objects. The reported judgments of “constant” or “variable” angular velocity were only slightly influenced by the projected angular velocities, but they were greatly affected by the variations of the deformation, a first-order component of the optic flow. When viewing either a rotating ellipsoidal volume or a planar surface that accelerated and decelerated over the course of rotation, observers’ tendencies to report a variable angular velocity were increased when the temporal phase of the acceleration pattern increased the range of variation of the median deformation; the tendencies were decreased when the same acceleration pattern was used to decrease the range of variation of the median deformation. These results provide evidence contrary to the hypothesis that the visual system performs a mathematically correct analysis of the optic flow.